This application relates generally to computer disc drives and more particularly to bottom mounting through a protective shield.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modem disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer diameter of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces. The actuator thus allows the head to move back and forth in an arcuate fashion between an inner radius and an outer radius of the discs.
A majority of the disc drive""s essential electronics are mounted on the printed circuit board assembly (xe2x80x9cPCBAxe2x80x9d). The PCBA is fastened to the bottom exterior surface of the drive and includes electrical components that manage the operations of the disc drive. For example, the PCBA includes electrical components that control the speed of the spindle and position of the actuator arms over the discs. Similarly, the PCBA also includes electrical components that interface with the computer""s processor.
Seagate Technology, the assignee of the present invention, has installed a metal cover, or shield plate, over the PCBA to protect the board, and hence the disc drive""s essential electronic circuitry, from electrostatic discharge. The cover also makes disc drive installation less time consuming and less likely to result in damage to the PCBA. However, it has been recognized that the ability of the electrical components on the PCBA to effectively dissipate heat generated during operation of the disc drive may be reduced for a number of reasons. One way to improve heat dissipation has been proposed by Bernett in the pending application entitled xe2x80x9cProtective Cover for a Disc Drive Printed Circuit Board,xe2x80x9d Ser. No. 09/506,525, filed on Feb. 17, 2000 now U.S. Pat. No. 6,320,728B1. The Bernett application discloses a PCBA protective cover that acts as a heat sink.
However, recent changes in the construction of disc drives have adversely impacted the ability to use PCBA covers. To reduce the hard shock pulse resulting in a topple drop test, mounting rails are frequently made shorter. When the mounting rails are reduced in height, the shield plate is the lowest part when the disc drive is bottom mounted. The shield plate is typically constructed from sheet metal and provides a cushion in the topple drop test. While having the shield plate as the lowest part is desirable in the topple drop test, it has undesirable effects in normal operation when the disc drive is bottom mounted.
Typically, when a disc drive with normal (full) height mounting rails is fastened to the mounting structure, the screws are tightened until the bottom mounting rails become intimate with the mounting structure. However, for a disc drive that has the reduced height bottom mounting rails, the reduced height makes the PCBA protective cover the lowest part in the disc drive envelope. As a result when the disc drive is mounted onto the mounting structure, the PCBA protective cover comes into contact with the mounting structure first. When the screws are tightened to secure the disc drive to the mounting structure, a compressive force is delivered to the PCBA protective cover. Undesirably, the compressive force is transmitted to the PCBA and has a detrimental effect on the functioning of the PCBA components.
Accordingly there is a need for a mounting assembly that relieves the compressive force from the baseplate on the PCBA.
Embodiments of the present invention solve the above and other problems by including shield plate mounting means that is separate and independent from the disc drive mounting means. An embodiment of the present invention provides a method and assembly for bottom mounting a disc drive to a mounting structure whereby a compressive force is not applied to the PCBA between the baseplate and a bottom shield plate.
The mounting assembly includes a shield plate covering the printed circuit board assembly positioned below the baseplate. The shield plate includes disc drive mounting flanges, each flange having a boss for receiving a disc drive mounting fastener for fastening the disc drive to the mounting structure. The mounting assembly further includes a pair of mounting rails on opposite sides of the baseplate and extending downward from the baseplate. The printed circuit board assembly is sandwiched between the two mounting rails. Each mounting rail includes notches. Each notch is aligned with and receives one of the disc drive mounting flanges of the shield plate. The notch provides a clearance region over the boss. The notch can further provide a clearance region over the disc drive mounting fastener when the fastener is filly extended through the mounting structure and into or through the boss.
The mounting method includes fastening the shield plate onto the baseplate of the disc drive via recessed regions in the shield plate having shield mounting holes. Shield mounting fasteners pass through the shield plate and into the baseplate to secure the shield plate to the baseplate. The method further includes separately fastening the shield plate onto the mounting structure by passing disc drive mounting fasteners from the mounting structure into bosses formed in flanges extending laterally outward on the sides of the shield plate. The method includes aligning the flanges with notches in base rails of the baseplate, whereby the notches receive the ends of the disc drive mounting fasteners and the fasteners do not extend into the baseplate. The method avoids compression of the PCBA between the baseplate and the shield plate by providing separate shield mounting and disc drive mounting steps.
These and various other features as well as advantages will be apparent from a reading of the following detailed description and a review of the associated drawings.